Currently, energy production in Korea heavily relies on fossil fuels that are almost all imported from foreign countries, but because of an increase in the use of fossil fuels and concern about the exhaustion thereof, raw material prices are increasing rapidly. The percentage of coal in the energy source for power generation in Korea in the year is 41.4%, which is higher than 33.2% for nuclear fuel and 19.2% for natural gas. Although domestic dependence on coal is high as described above, international coal prices are rising annually due to a global need for coal utilization together with rises in international oil prices, and thus the development of technology for efficient use of coal is needed. In addition, as the United Nations Convention on Climate Change receive global attention, coal power generation that can generate power in the most cost-effective manner receives as a main cause of carbon emissions, coal power generation technology has been studied in order to increase power generation efficiency while solving CO2 emission problems.
Meanwhile, fuel cells have received attention as energy conversion systems capable of substituting for internal combustion engines, and many studies thereon have been conducted. Among several kinds of fuel cells, a solid oxide fuel cell (SOFC) is operated at a high temperature of 600-1000° C., and thus has the highest power conversion efficiency and enables heat recovery and co-generation using good-quality waste heat, thereby increasing the efficiency of the entire power generation system. In addition, SOFC has advantages in that it does not need to use a noble metal catalyst, because it has high electrode activity due to its high operating temperature, and in that it can use various fuels, including hydrogen (H2), carbon monoxide (CO), and hydrocarbon fuels such as methane (CH4). Because of such advantages of high powder density and high efficiency, active studies on the use of SOFC for home power generation systems or distributed power generation systems have been conducted.
However, when methane or carbon monoxide is used as a fuel for SOFC, carbon is generated during its oxidation and decomposition. Particularly, when carbon monoxide alone is supplied as the fuel, carbon is deposited on the surface of a Ni-YSZ anode to reduce a space in which a reaction can occur. Therefore, a fuel cell having a new structure needs to be suggested which is capable of overcoming the problem associated with the reduction in fuel cell performance caused by this carbon deposition.
In addition, a coal gasification reaction is a reforming reaction consisting of a steam reforming reaction (C+H2O→CO+H2) and a carbon dioxide reforming reaction (C+CO2→2CO). This reforming reaction is an endothermic reaction that absorbs heat comparable to that absorbed by a combustion reaction (C+O2→CO2). Thus, in order to perform coal gasification (carbon reforming), a considerable amount of reaction heat should be provided. However, conventional coal gasifiers have shortcomings in that a coal reforming reaction is not satisfactorily achieved due to limited reaction temperature and in that the internal temperature of the coal gasifier is not uniformly maintained.